The present invention relates to apparatus for controlling the drafting mechanism of a sliver in a textile draw frame to reduce the variations in mass thereof, commonly referred to in the textile industry as an autoleveling apparatus, and more particularly to an arrangement for use in such apparatus for additionally compensating for operating parameters other than mass variations which also affect the sliver draft, such as physical characteristics of the sliver and environmental characteristics of the textile machine.
Known prior art is disclosed in U.S. patent application Ser. No. 69,247, entitled "A Method And Apparatus For Controlling The Drafting Of Sliver In A Drawing Frame" filed July 2, 1987, by Konig et al, of common overship which is the U.S. counterpart of West German patent applicaton P No. 36 22 584.3. This invention provides two sensing devices, one which senses the variations in the mass characteristics of sliver in advance of the drafting mechanism and another which senses the differences in mass per unit length of the sliver following the drafting mechanism. The sensed variations and differences are fed to a regulating device which generates a control signal to vary the draft of the drafting mechanism to compensate for variations in mass of sliver in response to the sensed variations in a time-delayed manner and for the difference of the sensed mass per unit length and a selectable theoretical value for mass per unit of length.
Additional prior art is disclosed in German unexamined application No. 30 35 196. This invention teaches a sensing device for sensing the sliver density and generating a signal to a regulating means. The regulating means generates an adjusting signal as a function of the silver density signal, the drawing-off speed of the sliver, and the speed of rotation of the drafting arrangement to control drafting arrangement so that the sliver produced is of a constant density.
Both of these prior art systems control the drafting of sliver in response to the sensing of variations in mass of the silver or variations in the density of the sliver prior to drafting and combining these sensed variations with other signals such as the sensed mass variations after drafting or the speed of rotation of the drafting arrangement but none of the prior art takes into consideration operating parameters other than variations in sliver mass or density, nor do they consider environmental conditions.